I have only seen one game this year, the first one vs NJ, but
who are the slow D ?

McGillis isn't slow is he ?
Jillson ?
Boyton?

These three I would say aren't speedsters, but are decent.

O'Donnell
Moran

These two I would say are average, or maybe a 1/2 step slow.

Gill = Slow.

Do the last 3 make the B's D slow overall , or is it just that the
B's are lacking that one truely offensive D'man to bring the puck up.

Does substituting Girard for Moran or Gill make this a fast D?

Make no mistake about it, speed on defense is a problem. The Bruins have to adjust their play because of it. For instance, when the play is in the offensive zone, the d-men have to be exceptionally aware of when to fall back. The reason is because they need to keep distance between the oncoming forwards due to the speed of the break out. That inhibits certain offensive opportunities. I could see this in the B's/Duck's game, there was one time Samsonov had the puck above the circles and he needed to drop it off to the point, but those guys had to fall back just in case there was a turnover.

Another critical factor is when the opponent is coming through the nuetral zone with speed. The B's try to limit this from happening via the trap, but when it occurs the Bruins defensemen are forced to give up the blueline. This enables much more creativity for the opponent to skate deeper or make a pass. Furthermore, it can spread out the play and create the kind of havoc which produces turnovers. You always have to be cognizant of the space between your forwards and defensemen. When there are gaps, a few things happen. One, there is more open ice for the opponent to utilize. Again, this can give him room for creativity which can result in defensive breakdowns. Two, the forwards cannot backcheck as easy and can get left out of position.

Also, with a slower defense, it's more difficult to execute 1-1 coverages in your own zone. This is critical with today's emphasis on speed and limited obstruction. Forwards have more lee-way to operate freely in the offensive zone, so the 1-1 coverage is magnified. Simply put, if you don't have much skill or quickness on your defense, then it's much more difficult to stay with these quick skilled forwards. In turn, that means there will be breakdowns caused when a guy gets beat. Someone will have to move out of position and boom, a prime scoring opportunity can be handed to the opponent. The Bruins have varying degrees of ability in this regard.

Lastly, there's the transition and offensive potential. Who sets the tone and carries the puck up ice from behind the net? The puck rushing defenseman. This can have a dramatic effect on the game. The guy who can do this forces the opposition to fall back from their triangle forecheck set up down low. It creates movement all over the ice, and when there's movement, things happen. Not only this, but when the Bruins forwards hit the offensive blueline with speed, the high man, usually a trailing defenseman, can swoop in and look for backdoor goals. This can create chaos for the opposition. The Bruins have some of this abiltiy in Jillson and Boynton, so they are not completely void, but with a speedy a player who has the uncanny ability to dart in quickly such as Berard or Girard, they would have more offensive potential.

So, make no mistake about the impact of speed and skill on your defense. As of now, the Bruins have benefitted by tightening up their play through the nuetral zone and keeping reasonable space between their defensemen and oncoming forwards. Without the trap, the Bruins would suffer a higher GAA...